Lately, Very Large Scale Integrated Circuit elements have become more highly integrated, and require a more dust-free manufacturing system. Especially, in a transporting system, not only dust-free environment but also long service life are necessary. For this reason, a magnetic floating transporting system is being developed as a wafer transporting system for use in manufacturing apparatus for the next generation semi-conductor.
The magnetic floating transporting system first floats a carrier device loaded with wafers and holds the carrier device in a floated position by virtue of magnetic force of electric magnets, then transports the carrier device without any contacts between surroundings by utilizing a linear motor mechanism for example. Since wafers can be transported in a sealed vacuum tunnel or in a clean tunnel filled with clean nitrogen gas atmosphere without making contacts with surrounding elements, this magnetic transporting system does not generate any dust troubles and is capable of realizing a highly clean transporting system. At certain locations of the clean tunnel, the magnetic floating transporting system is combined with processing apparatus such as photo-lithography device or ion plating apparatus, and the transported wafers will be carried to these processing apparatus to be processed.
Even in such combined systems comprising the processing apparatus and the wafer transporting apparatus, wafers must be stored outside of the system, or must be stored in or carried through the ambient air while they are being moved toward other systems. The present applicant has developed a technique for storing and transporting the wafers in a tightly sealed box having a highly clean inner atmosphere such as a vacuum, and has filed a patent application therefor (Japanese Patent Application, No. Heisei-4-290817).
However, although the wafers may be retained in a tightly sealed box having a clean atmosphere, and carried through the ambient air to be moved to the tunnel-type magnetic transporting system, and transferred to and transported by a carrier arranged in a tightly sealed space, at least the outer surface of the box is carried into the clean tunnel, when they are entering the clean tunnel of the magnetic transporting system.
Therefore, although the clean tunnel of the processing apparatus and transporting system are kept in highly clean atmospheres such as vacuum, there is still a problem of generating secondary contamination sources because the box may carry into the tunnel some contaminating particles or molecules, which stick to the outer surface of the box during transportation or storage in the ambient air.
Further, since the box containing wafers in an atmosphere, such as a vacuum, does not include an exhausting apparatus, there is a problem that the vacuum will be lost gradually. Moreover, there was a problem of outer air contaminations entering through vacuum sealing materials or by leakage through walls.